Any edit that changes content in a way that deliberately compromises the integrity of Wikipedia is considered vandalism. The most common and obvious types of vandalism include insertion of obscenities and crude humor. Vandalism can also include advertising language, and other types of spam.[48] Sometimes editors commit vandalism by removing information or entirely blanking a given page. Less common types of vandalism, such as the deliberate addition of plausible but false information to an article, can be more difficult to detect. Vandals can introduce irrelevant formatting, modify page semantics such as the page's title or categorization, manipulate the underlying code of an article, or utilize images disruptively.[49]

White-haired elderly gentleman in suit and tie speaks at a podium.

John Seigenthaler has described Wikipedia as "a flawed and irresponsible research tool".[50]
Obvious vandalism is generally easy to remove from wiki articles; in practice, the median time to detect and fix vandalism is a few minutes.[19][20] However, in one high-profile incident in 2005, false information was introduced into the biography of American political figure John Seigenthaler and remained undetected for four months.[50] He was falsely accused of being a suspect in the assassination of John F. Kennedy by an anonymous user, but was actually an administrative assistant to President Kennedy.[50] Seigenthaler, the founding editorial director of USA Today and founder of the Freedom Forum First Amendment Center at Vanderbilt University, called Wikipedia co-founder Wales and asked whether he had any way of knowing who contributed the misinformation. Wales replied that he did not, although the perpetrator was eventually traced.[51][52] This incident led to policy changes on the site, specifically targeted at tightening up the verifiability of all biographical articles of living people.[53]

Rules and laws governing content and editor behavior

Content in Wikipedia is subject to the laws (in particular, the copyright laws) of the United States and of the US state of Virginia, where the majority of Wikipedia's servers are located. Beyond legal matters, the editorial principles of Wikipedia are embodied in the "five pillars", and numerous policies and guidelines that are intended to shape the content appropriately. Even these rules are stored in wiki form, and Wikipedia editors as a community write and revise the website's policies and guidelines.[54] Editors can enforce these rules by deleting or modifying non-compliant material. Originally, rules on the non-English editions of Wikipedia were based on a translation of the rules on the English Wikipedia. They have since diverged to some extent.